Explanation:

- The initial mixture is 85 litres with the alcohol to water ratio of 11:6.

- Calculate the volume of alcohol:

$$

\frac{11}{17} \times 85 = 55 \text{ litres}

$$

- Calculate the volume of water:

$$

\frac{6}{17} \times 85 = 30 \text{ litres}

$$

- Let \( x \) be the litres of water to add. The new water volume will be \( 30 + x \).

- The new total mixture becomes \( 85 + x \).

- Set up the ratio equation for the new desired ratio (5:3):

$$

\frac{55}{30 + x} = \frac{5}{3}

$$

- Solve for \( x \):

$$

5(30 + x) = 3 \times 55

$$

$$

150 + 5x = 165

$$

$$

5x = 15

$$

$$

x = 3

$$

- The correct answer is Option 2: 3 litres

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